Re: [PATCH v3] xfs_io: copy_range don't truncate dst_file, and add smart length

[Eric Sandeen <sandeen@sandeen.net>]

On 9/9/19 2:29 AM, Jianhong.Yin wrote:
> 1. copy_range should be a simple wrapper for copy_file_range(2)
> and nothing else. and there's already -t option for truncate.
> so here we remove the truncate action in copy_range.
> see: https://patchwork.kernel.org/comment/22863587/#1
> 
> 2. improve the default length value generation:
> if -l option is omitted use the length that from src_offset to end
> (src_file's size - src_offset) instead.
> if src_offset is greater than file size, length is 0.
> 
> 3. update manpage
> 
> 4. rename var name from 'src, dst' to 'src_off, dst_off'
> 
> and have confirmed that this change will not affect xfstests.
> 
> Signed-off-by: Jianhong Yin <yin-jianhong@163.com>

Reviewed-by: Eric Sandeen <sandeen@redhat.com>

> ---
>  io/copy_file_range.c | 40 ++++++++++++++--------------------------
>  man/man8/xfs_io.8    | 12 ++++++------
>  2 files changed, 20 insertions(+), 32 deletions(-)
> 
> diff --git a/io/copy_file_range.c b/io/copy_file_range.c
> index b7b9fd88..c2105115 100644
> --- a/io/copy_file_range.c
> +++ b/io/copy_file_range.c
> @@ -36,12 +36,12 @@ copy_range_help(void)
>   * glibc buffered copy fallback.
>   */
>  static loff_t
> -copy_file_range_cmd(int fd, long long *src, long long *dst, size_t len)
> +copy_file_range_cmd(int fd, long long *src_off, long long *dst_off, size_t len)
>  {
>  	loff_t ret;
>  
>  	do {
> -		ret = syscall(__NR_copy_file_range, fd, src, file->fd, dst,
> +		ret = syscall(__NR_copy_file_range, fd, src_off, file->fd, dst_off,
>  				len, 0);
>  		if (ret == -1) {
>  			perror("copy_range");
> @@ -66,21 +66,13 @@ copy_src_filesize(int fd)
>  	return st.st_size;
>  }
>  
> -static int
> -copy_dst_truncate(void)
> -{
> -	int ret = ftruncate(file->fd, 0);
> -	if (ret < 0)
> -		perror("ftruncate");
> -	return ret;
> -}
> -
>  static int
>  copy_range_f(int argc, char **argv)
>  {
> -	long long src = 0;
> -	long long dst = 0;
> +	long long src_off = 0;
> +	long long dst_off = 0;
>  	size_t len = 0;
> +	bool len_specified = false;
>  	int opt;
>  	int ret;
>  	int fd;
> @@ -93,15 +85,15 @@ copy_range_f(int argc, char **argv)
>  	while ((opt = getopt(argc, argv, "s:d:l:f:")) != -1) {
>  		switch (opt) {
>  		case 's':
> -			src = cvtnum(fsblocksize, fssectsize, optarg);
> -			if (src < 0) {
> +			src_off = cvtnum(fsblocksize, fssectsize, optarg);
> +			if (src_off < 0) {
>  				printf(_("invalid source offset -- %s\n"), optarg);
>  				return 0;
>  			}
>  			break;
>  		case 'd':
> -			dst = cvtnum(fsblocksize, fssectsize, optarg);
> -			if (dst < 0) {
> +			dst_off = cvtnum(fsblocksize, fssectsize, optarg);
> +			if (dst_off < 0) {
>  				printf(_("invalid destination offset -- %s\n"), optarg);
>  				return 0;
>  			}
> @@ -112,6 +104,7 @@ copy_range_f(int argc, char **argv)
>  				printf(_("invalid length -- %s\n"), optarg);
>  				return 0;
>  			}
> +			len_specified = true;
>  			break;
>  		case 'f':
>  			src_file_nr = atoi(argv[1]);
> @@ -137,7 +130,7 @@ copy_range_f(int argc, char **argv)
>  		fd = filetable[src_file_nr].fd;
>  	}
>  
> -	if (src == 0 && dst == 0 && len == 0) {
> +	if (!len_specified) {
>  		off64_t	sz;
>  
>  		sz = copy_src_filesize(fd);
> @@ -145,16 +138,11 @@ copy_range_f(int argc, char **argv)
>  			ret = 1;
>  			goto out;
>  		}
> -		len = sz;
> -
> -		ret = copy_dst_truncate();
> -		if (ret < 0) {
> -			ret = 1;
> -			goto out;
> -		}
> +		if (sz > src_off)
> +			len = sz - src_off;
>  	}
>  
> -	ret = copy_file_range_cmd(fd, &src, &dst, len);
> +	ret = copy_file_range_cmd(fd, &src_off, &dst_off, len);
>  out:
>  	close(fd);
>  	return ret;
> diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
> index 6e064bdd..61c35c8e 100644
> --- a/man/man8/xfs_io.8
> +++ b/man/man8/xfs_io.8
> @@ -669,13 +669,13 @@ The source must be specified either by path
>  or as another open file
>  .RB ( \-f ).
>  If
> -.I src_file
> -.IR src_offset ,
> -.IR dst_offset ,
> -and
>  .I length
> -are omitted the contents of src_file will be copied to the beginning of the
> -open file, overwriting any data already there.
> +is not specified, this command copies data from
> +.I src_offset
> +to the end of
> +.BI src_file
> +into the dst_file at
> +.IR dst_offset .
>  .RS 1.0i
>  .PD 0
>  .TP 0.4i
>